The present invention relates to a portable service unit for servicing a refrigeration circuit and particularly to an apparatus for unloading a supply tank of refrigerant from a weight sensor when the service unit is being transported.
Portable carts are used in connection with servicing refrigeration circuits, such as the air conditioning unit of a vehicle. The portable machines include hoses which are coupled to the refrigeration circuit to be serviced. A vacuum pump and compressor operate to recover refrigerant from the vehicle's air conditioning unit, separate contaminants and oil from the recovered charge, flush the unit, and subsequently recharge the system from a supply of either recovered refrigerant and/or new refrigerant from a main refrigerant tank. U.S. Pat. No. 4,441,330 discloses one such apparatus.
In the past, when the supply of refrigerant would run low, a display system associated with the equipment would prompt the operator to connect an external tank and refill the refrigerant supply. This resulted in a time-consuming and potentially error-prone system by which a servicing cycle can be interrupted by the lack of adequate refrigerant or refrigerant could inadvertently escape to the atmosphere during the refilling of the refrigerant supply tank.
In order to overcome the problem with an interrupted supply of refrigerant, an automatic tank refilling system which detects the weight of refrigerant in a main tank and provides an auxiliary tank, which supplies refrigerant to the main tank when the main tank refrigerant becomes low, is disclosed in concurrently filed U.S. patent application Ser. No. 09/272789, filed concurrently herewith, entitled BACKGROUND TANK FILL, the disclosure of which is incorporated herein by reference. This improved system for maintaining refrigerant in the primary or main refrigerant supply tank relies upon the main tank resting upon a weight sensor such that the weight of refrigerant in the main tank can be monitored during a servicing cycle of a refrigeration circuit. In order to accurately measure the tank weight, the tank rests upon a weight sensitive detector such as a load cell which is a relatively sensitive device subject to misalignment, miscalibration or even damage when the portable cart to which the servicing apparatus is mounted is transported either from one vehicle to another or from one part of the service area to another.
There exists a need, therefore, for a system to protect the weight sensor, such as a load cell, incorporated to provide signals for controlling the level of refrigerant in the main refrigerant supply tank during movement of the servicing cart.